This invention relates generally to sheet feed machines, and particularly to the type of machines which feed sheets from the bottom of a stack successively into an ancillary machine such as a printer for processing.
There are many types of machines and printers that successively process individual sheets of materials such as envelopes, book pages, pamphlets and the like. The sheets are individually fed into the printer from a stack as by the use of suction cups which descend atop the uppermost member of the stack at an input feed station and lift the uppermost member off and into the printer. The sheet material may be manually replaced with a successive stack once the stack at the printer input feed station is exhausted. Such manual replacement of material, however, requires that the printer itself be momentarily shut down and the sheet gripping mechanism moved aside during stack replenishing. This intermittent halting and restarting of printing operations has the obvious disadvantage of limiting the speed at which the sheet material may be printed.
To overcome the just mentioned problem sheet feed machines have heretofore been devised which may be connected to the input feed station of a printing machine. The main function of the sheet input machine is to provide a place in which stacks of sheet material may be replenished without interrupting the operation of the printer. With these sheet feed machines the lowermost sheets are successively stripped from the bottom of the stack and fed into the printer input station.
Unfortunately, the just described sheet feed machines have possessed limitations and persistent problems. Foremost among these has been the difficulty encountered in coordinating or timing the speed at which the sheet feed machine operates with that at which the printer itself operates. Slight mismatches in timing present errors which are cumulative over periods of time which can quickly lead to erroneous printing. In addition, these sheet feeders have lacked versatility with regard to material handling capability. In those case where sheets have been fed with adjacent sheets in a mutually overlapped condition the machines have tended to vary the degree of overlap beyond acceptable limits. In addition, even where the initial overlap and speed has been correct the machine has experienced difficulty in maintaining proper spacing along the path at which they are conveyed to the printer. The time and difficulty encountered in correctly attaching the feeder to the printers has also been substantial.
Accordingly, it is a general object of the present invention to provide an improved sheet feed machine.
More specifically, it is an object of the present invention to provide a sheet feed machine whose speed of operations does not have to be closely timed with that of an ancillary sheet processing machine which it serves.
Another object of the invention is to provide a sheet feed machine of the type described with improved means for stripping sheets from the bottom of the stack of sheets with adjacent stripped sheets in a mutually overlapped configuration.
Yet another object of the invention is to provide the sheet feed machine of the type described with improved means for holding a stream of sheets in relative position one to another as they are being fed.
Still another object of the invention is to provide a sheet feed machine that may be quickly and easily attached to the sheet processing machine which it serves.